A North American Union is a threat to American sovereignty, but the highway is just a conduit for trade. That might be bad for domestic business, but it isn't a direct threat on sovereignty, and isn't much of an indirect threat either.
(The picture was unnecessary; just used it to inaugurate the use of [faces] to help express comments to help reduce the odds that they'll be misconstrued).
Do you know if Texas funded the road?
Well it means the seizure of one heck of a lot of land. They are not planning a mere road. The Texas segment of the project is called the "Trans Texas Corridor" and is proposed to include a wide strip land on either side which will be used for economic development along the road.
It's a huge vanity project for the Govenor. I don't know if any other states have bought into this NAFT superhighway idea (which was supposed to create a corridor all the way to Canada). Texas has a political faction that has bought into it in a big way though.
Well, not quite, since they would not have to go through customs until Kansas City. Also the traffic counts there certainly do not warrant such an undertaking. Even in 2025, most rural sections of I-35 will still only need 6 lanes at the most (including the last 150 miles to the Mexican border in Texas which will still only need 4 lanes, which makes NAFTA hardly a real reason for the problems). As for the link to Canada - that is currently a 2 lane highway!